Unlike general vacuum drying, according to the present invention, pressure is generated by means of a fan that sucks air to attain a pressure of 980 hPa, moisture in the original material is uniformly evaporated, and the evaporated moisture is also discharged to the outside by the fan. With this configuration, it is possible to manufacture a snack, having the same shape as a slice of the citrus fruit produced using a slicing machine, without loss of flavor, nutrition, and so on.